The present invention relates to a gene useful as an indicator in the prophylaxis, diagnosis and treatment of diseases in humans. More particularly, it relates to a novel human gene analogous to rat, mouse, yeast, nematode and known human genes, among others, and utilizable, after cDNA analysis thereof, chromosome mapping of cDNA and function analysis of cDNA, in gene diagnosis using said gene and in developing a novel therapeutic method.
The genetic information of a living thing has been accumulated as sequences (DNA) of four bases, namely A, C, G and T, which exist in cell nuclei. Said genetic information has been preserved for line preservation and ontogeny of each individual living thing.
In the case of human being, the number of said bases is said to be about 3 billion (3xc3x97109) and supposedly there are 50 to 100 thousand genes therein. Such genetic information serves to maintain biological phenomena in that regulatory proteins, structural proteins and enzymes are produced via such route that mRNA is transcribed from a gene (DNA) and then translatedinto a protein. Abnormalities in said route from gene to protein translation are considered to be causative of abnormalities of life supporting systems, for example in cell proliferation and differentiation, hence causative of various diseases.
As a result of gene analyses so far made, a number of genes -which may be expected to serve as useful materials in drug development, have been found, for example genes for various receptors such as insulin receptor and LDL receptor, genes involved in cell proliferation and differentiation and genes for metabolic enzymes such as proteases, ATPase and superoxide dismutases.
However, analysis of human genes and studies of the functions of the genes analyzed and of the relations between the genes analyzed and various diseases have been just begun and many points remain unknown. Further analysis of novel genes, analysis of the functions thereof, studies of the relations between the genes analyzed and diseases, and studies for applying the genes analyzed to gene diagnosis or for medicinal purposes, for instance, are therefore desired in the relevant art.
If such a novel human gene as mentioned above can be provided, it will be possible to analyze the level of expression thereof in each cell and the structure and function thereof and, through expression product analysis and other studies, it may become possible to reveal the pathogenesis of a disease associated therewith, for example a genopathy or cancer, or diagnose and treat said disease, for instance. It is an object of the present invention to provide such a novel human gene.
For attaining the above object, the present inventors made intensive investigations and obtained the findings mentioned below. Based thereon, the present invention has now been completed.
Thus, the present inventors synthesized cDNAs based on mRNAs extracted from various tissues, inclusive of human fetal brain, adult blood vessels and placenta, constructed libraries by inserting them into vectors, allowing colonies of Escherichia coli transformed with said libraries to form on agar medium, picked up colonies at random and transferred to 96-well micro plates and registered a large number of human gene-containing E. coli clones.
Each clone thus registered was cultivated on a small size, DNA was extracted and purified, the four base-specifically terminating extension reactions were carried out by the dideoxy chain terminator method using the cDNA extracted as a template, and the base sequence of the gene was determined over about 400 bases from the 5xe2x80x2 terminus thereof using an automatic DNA sequencer. Based on the thus-obtained base sequence information, a novel family gene analogous to known genes of animal and plant species such as bacteria, yeasts, nematodes, mice and humans was searched for.
The method of the above-mentioned cDNA analysis is detailedly described in the literature by Fujiwara, one of the present inventors [Fujiwara, Tsutomu, Saibo Kogaku (Cell Engineering), 14, 645-654 (1995)].
Among this group, there are novel receptors, DNA binding domain-containing transcription regulating factors, signal transmission system factors, metabolic enzymes and so forth. Based on the homology of the novel gene of the present invention as obtained by gene analysis to the genes analogous thereto, the product of the gene, hence the function of the protein, can approximately be estimated by analogy. Furthermore, such functions as enzyme activity and binding ability can be investigated by inserting the candidate gene into an expression vector to give a recombinant.
According to the present invention, there are provided a novel human gene characterized by containing a nucleotide sequence coding for an amino acid sequence defined by SEQ ID NO:1, :4, :7, :10, :13, :16, :19, :22, :25, :28, :31, :34, :37 or 40, a human gene characterized by containing the nucleotide sequence defined by SEQ ID NO:2, :5, :8, :11, :14, :17, :20, :23, :26, :29, :32, :35, :38 or :41, respectively coding for the amino acid sequence mentioned above, and a novel human gene characterized by the nucleotide sequence defined by SEQ ID NO:3, :6, :9, :12, :15, :18, :21, :24, :27, :30, :33, :36, :39 or :42.
The symbols used herein for indicating amino acids, peptides, nucleotides, nucleotide sequences and so on are those recommended by IUPAC and IUB or in xe2x80x9cGuide-line for drafting specifications etc. including nucleotide sequences or amino acid sequencesxe2x80x9d (edited by the Japanese Patent Office), or those in conventional use in the relevant field of art.
As specific examples of such gene of the present invention, there may be mentioned genes deducible from the DNA sequences of the clones designated as xe2x80x9cGEN-501D08xe2x80x9d, xe2x80x9cGEN-080G01xe2x80x9d, xe2x80x9cGEN-025F07xe2x80x9d, xe2x80x9cGEN-076C09xe2x80x9d, xe2x80x9cGEN-331G07xe2x80x9d, xe2x80x9cGEN-163D09xe2x80x9d, xe2x80x9cGEN-078D05TA13xe2x80x9d, xe2x80x9cGEN-423A12xe2x80x9d, xe2x80x9cGEN-092E10xe2x80x9d, xe2x80x9cGEN-428B12xe2x80x9d, xe2x80x9cGEN-073E07xe2x80x9d, xe2x80x9cGEN-093E05xe2x80x9d and xe2x80x9cGEN-077A09xe2x80x9d shown later herein in Examples 1 to 11. The respective nucleotide sequences are as shown in the sequence listing.
These clones have an open reading frame comprising nucleotides (nucleic acid) respectively coding for the amino acids shown in the sequence listing. Their molecular weights were calculated at the values shown later herein in the respective examples. Hereinafter, these human genes of the present invention are sometimes referred to as the designation used in Examples 1 to 11.
In the following, the human gene of the present invention is described in further detail.
As mentioned above, each human gene of the present invention is analogous to rat, mouse, yeast, nematode and known human genes, among others, and can be utilized in human gene analysis based on the information about the genes analogous thereto and in studying the function of the gene analyzed and the relation between the gene analyzed and a disease. It is possible to use said gene in gene diagnosis of the disease associated therewith and in exploitation studies of said gene for medicinal purposes.
The gene of the present invention is represented in terms of a single-stranded DNA sequence, as shown under SEQ ID NO:2. It is to be noted, however, that the present invention also includes a DNA sequence complementary to such a single-stranded DNA sequence and a component comprising both. The sequence of the gene of the present invention as shown under SEQ ID NO:3nxe2x88x921 (where n is an integer of 1 to 14) is merely an example of the codon combination encoding the respective amino acid residues. The gene of the present invention is not limited thereto but can of course have a DNA sequence in which the codons are arbitrarily selected and combined for the respective amino acid residues. The codon selection can be made in the conventional manner, for example taking into consideration the codon utilization frequencies in the host to be used [Nucl. Acids Res., 9, 43-74 (1981)].
The gene of the present invention further includes DNA sequences coding for functional equivalents derived from the amino acid sequence mentioned above by partial amino acid or amino acid sequence substitution, deletion or addition. These polypeptides may be produced by spontaneous modification (mutation) or may be obtained by posttranslational modification or by modifying the natural gene (of the present invention) by a technique of genetic engineering, for example by site-specific mutagenesis [Methods in Enzymology, 154, p. 350, 367-382 (1987); ibid., 100, p. 468 (1983); Nucleic Acids Research, 12, p. 9441 (1984); Zoku Seikagaku Jikken Koza (Sequel to Experiments in Biochemistry) 1, xe2x80x9cIdensi Kenkyu-ho (Methods in Gene Research) IIxe2x80x9d, edited by the Japan Biochemical Society, p. 105 (1986) or synthesizing mutant DNAs by a chemical synthetic technique such as the phosphotriester method or phosphoamidite method [J. Am. Chem. Soc., 89, p. 4801 (1967); ibid., 91, p. 3350 (1969); Science, 150, p. 178 (1968); Tetrahedron Lett., 22, p. 1859 (1981); ibid., 24, p. 245 (1983)], or by utilizing the techniques mentioned above in combination.
The protein encoded by the gene of the present invention can be expressed readily and stably by utilizing said gene, for example inserting it into a vector for use with a microorganism and cultivating the microorganism thus transformed.
The protein obtained by utilizing the gene of the present invention can be used in specific antibody production. In this case, the protein producible in large quantities by the genetic engineering technique mentioned above can be used as the component to serve as an antigen. The antibody obtained may be polyclonal or monoclonal and can be advantageously used in the purification, assay, discrimination or identification of the corresponding protein.
The gene of the present invention can be readily produced based on the sequence information thereof disclosed herein by using general genetic engineering techniques [cf. e.g. Molecular Cloning, 2nd Ed., Cold Spring Harbor Laboratory Press (1989); Zoku Seikagaku Jikken Koza, xe2x80x9cIdenshi Kenkyu-ho I, II and IIIxe2x80x9d, edited by the Japan Biochemical Society (1986)].
This can be achieved, for example, by selecting a desired clone from a human cDNA library (prepared in the conventional manner from appropriate cells of origin in which the gene is expressed) using a probe or antibody specific to the gene of the present invention [e.g. Proc. Natl. Acad. Sci. USA, 78, 6613 (1981); Science, 222, 778 (1983)].
The cells of origin to be used in the above method are, for example, cells or tissues in which the gene in question is expressed, or cultured cells derived therefrom. Separation of total RNA, separation and purification of mRNA, conversion to (synthesis of) cDNA, cloning thereof and so on can be carried out by conventional methods. cDNA libraries are also commercially available and such cDNA libraries, for example various cDNA libraries available from Clontech Lab. Inc. can also be used in the above method.
Screening of the gene of the present invention from these cDNA libraries can be carried out by the conventional method mentioned above. These screening methods include, for example, the method comprising selecting a cDNA clone by immunological screening using an antibody specific to the protein produced by the corresponding cDNA, the technique of plaque or colony hybridization using probes selectively binding to the desired DNA sequence, or a combination of these. As regards the probe to be used here, a DNA sequence chemically synthesized based on the information about the DNA sequence of the present invention is generally used. It is of course possible to use the gene of the present invention or fragments thereof as the proble.
Furthermore, a sense primer and an antisense primer designed based on the information about the partial amino acid sequence of a natural extract isolated and purified from cells or a tissue can be used as probes for screening.
For obtaining the gene of the present invention, the technique of DNA/RNA amplification by the PCR method [Science, 230, 1350-1354 (1984)] can suitably be employed. Particularly when the full-length cDNA can hardly be obtained from the library, the RACE method (rapid amplification of cDNA ends; Jikken Igaku (Experimental Medicine), 12 (6), 35-38 (1994)], in particular the 5xe2x80x2 RACE method [Frohman, M. A., et al., Proc. Natl. Acad. Sci. USA, 85, 8998-9002 (1988)] is preferably employed. The primers to be used in such PCR method can be appropriately designed based on the sequence information of the gene of the present invention as disclosed herein and can be synthesized by a conventional method.
The amplified DNA/RNA fragment can be isolated and purified by a conventional method as mentioned above, for example by gel electrophoresis.
The nucleotide sequence of the thus-obtained gene of the present invention or any of various DNA fragments can be determined by a conventional method, for example the dideoxy method [Proc. Natl. Acad. Sci. USA, 74, 5463-5467 (1977)] or the Maxam-Gilbert method [Methods in Enzymology, 65, 499 (1980)]. Such nucleotide sequence determination can be readily performed using a commercially available sequence kit as well.
When the gene of the present invention is used and conventional techniques of recombinant DNA technology [see e.g. Science, 224, p. 1431 (1984); Biochem. Biophys. Res. Comm., 130, p. 692 (1985); Proc. Natl. Acad. Sci. USA, 80, p. 5990 (1983) and the references cited above] are followed, a recombinant protein can be obtained. More detailedly, said protein can be produced by constructing a recombinant DNA enabling the gene of the present invention to be expressed in host cells, introducing it into host cells for transformation thereof and cultivating the resulting transformant.
In that case, the host cells may be eukaryotic or prokaryotic. The eukaryotic cells include vertebrate cells, yeast cells and so on, and the vertebrate cells include, but are not limited to, simian cells named COS cells [Cell, 23, 175-182 (1981)], Chinese hamster ovary cells and a dihydrofolate reductase-deficient cell line derived therefrom [Proc. Natl. Acad. Sci. USA, 77, 4216-4220 (1980)] and the like, which are frequently used.
As regards the expression vector to be used with vertebrate cells, an expression vector having a promoter located upstream of the gene to be expressed, RNA splicing sites, a polyadenylation site and a transcription termination sequence can be generally used. This may further have an origin of replication as necessary. As an example of said expression vector, there may be mentioned pSV2dhfr [Mol. Cell. Biol., 1, 854 (1981)], which has the SV40 early promoter. As for the eukaryotic microorganisms, yeasts are generally and frequently used and, among them, yeasts of the genus Saccharomyces can be used with advantage. As regards the expression vector for use with said yeasts and other eukaryotic microorganisms, pAM82 [Proc. Natl. Acad. Sci. USA, 80, 1-5 (1983)], which has the acid phosphatase gene promoter, for instance, can be used.
Furthermore, a prokaryotic gene fused vector can be preferably used as the expression vector for the gene of the present invention. As specific examples of said vector, there may be mentioned pGEX-2TK and pGEX-4T-2 which have a GST domain (derived from S. japonicum) with a molecular weight of 26,000.
Escherichia coli and Bacillus subtilis are generally and preferably used as prokaryotic hosts. When these are used as hosts in the practice of the present invention, an expression plasmid derived from a plasmid vector capable of replicating in said host organisms and provided in this vector with a promoter and the SD (Shine and Dalgarno) sequence upstream of said gene for enabling the expression of the gene of the present invention and further provided with an initiation codon (e.g. ATG) necessary for the initiation of protein synthesis is preferably used. The Escherichia coli strain K12, among others, is preferably used as the host Escherichia coli, and pBR322 and modified vectors derived therefrom are generally and preferably used as the vector, while various known strains and vectors can also be used. Examples of the promoter which can be used are the tryptophan (trp) promoter, lpp promoter, lac promoter and PL/PR promoter.
The thus-obtained desired recombinant DNA can be introduced into host cells for transformation by using various general methods. The transformant obtained can be cultured by a conventional method and the culture leads to expression and production of the desired protein encoded by the gene of the present invention. The medium to be used in said culture can suitably be selected from among various media in conventional use according to the host cells employed. The host cells can be cultured under conditions suited for the growth thereof.
In the above manner, the desired recombinant protein is expressed and produced and accumulated or secreted within the transformant cells or extracellularly or on the cell membrane.
The recombinant protein can be separated and purified as desired by various separation procedures utilizing the physical, chemical and other properties thereof [cf. e.g. xe2x80x9cSeikagaku (Biochemistry) Data Book IIxe2x80x9d, pages 1175-1259, 1st Edition, 1st Printing, published Jun. 23, 1980 by Tokyo Kagaku Dojin; Bio-chemistry, 25 (25), 8274-8277 (1986); Eur. J. Biochem., 163, 313-321 (1987)]. Specifically, said procedures include, among others, ordinary reconstitution treatment, treatment with a protein precipitating agent (salting out), centrifugation, osmotic shock treatment, sonication, ultrafiltration, various liquid chromatography techniques such as molecular sieve chromatography (gel filtration), adsorption chromatography, ion exchange chromatography, affinity chromatography and high-performance liquid chromatography (HPLC), dialysis and combinations thereof. Among them, affinity chromatography utilizing a column with the desired protein bound thereto is particularly preferred.
Furthermore, on the basis of the sequence information about the gene of the present invention as revealed by the present invention, for example by utilizing part or the whole of said gene, it is possible to detect the expression of the gene of the present invention in various human tissues. This can be performed by a conventional method, for example by RNA amplification by RT-PCR (reverse transcribed-polymerase chain reaction) [Kawasaki, E. S., et al., Amplification of RNA, in PCR Protocol, A guide to methods and applications, Academic Press, Inc., San Diego, 21-27 (1991)], or by northern blotting analysis [Molecular Cloning, Cold Spring Harbor Laboratory (1989)], with good results.
The primers to be used in employing the above-mentioned PCR method are not limited to any particular ones provided that they are specific to the gene of the present invention and enable the gene of the present invention alone to be specifically amplified. They can be designed or selected apropriately based on the gene information provided by the present invention. They can have a partial sequence comprising about 20 to 30 nucleotides according to the established practice. Suitable examples are as shown in Examples 1 to 11.
Thus, the present invention also provides primers and/or probes useful in specifically detecting such novel gene.
By using the novel gene provided by the present invention, it is possible to detect the expression of said gene in various tissues, analyze the structure and function thereof and, further, produce the human protein encoded by said gene in the manner of genetic enginnering. These make it possible to analyze the expression product, reveal the pathology of a disease associated therewith, for example a genopathy or cancer, and diagnose and treat the disease.